Piston



Oct. 11, 1938.

c. GIA. ROSEN 2,132,805

PISTON Original Filed Aug. 8, 1933 3 S etseet 1 J INVENTOR.

CARL 6.1L Foss/v B Y A TTORNE Y.

' Oct. 11, 1-938. c. G. A. ROSEN PISTON s Sheets-Sheet 2 Original Filed Aug. 8, 1933 2N m m 8 mm? i v q 1 k x 2w U mm fin a. w h wk Q Q QM QM N m m am m g CARL. 6. A. Ross/v M A TTORNE Y.

patentedv Oct. 11, 1938 UNITED STATE PISTON Carl G. A. Bosn,

Caterpillar Tractor (70.,

Oakland, Calif., assignor to San Leandro, Calif.,-a

corporation of California Original applicationAugust *8, 1933, Serial No. 684,179. Divided and this application October her 11, 1937,

1 6 Claims.

My invention relates to internal combustion engines and more particularly to an improved piston for use in such This application is a engines.

Serial No. 684,179, filed August 8, 1933, and assigned to the Caterpillar Tractor Co., assignee of the present application.

To maintain similarity between this divisional application and the originates, practical to obtain 0 responds to the pertinent case, and the reference characters, .respond in-both cases.

In internal combustion engines, more particularly those of the wherein fuel under pressure is inder and ignited by 00 volume and contour formed between the play an important p bustion characteristics of tween the injected m cylinder. The ideal obtain smooth but r air, with sufficient air present to enable completethe descriptive parent case fromwhich it matter, in so far as ontinuity and clearance corportions of the parent likewise corcompression ignition type,

injected into a cylheat of compression, the of the combustion chamber piston and the cylinder head art in determining the comthe mixture formed befuel and the air in the, condition strived for isto apid mixing of the fuel and combustion of the fuel. With this condition real- .ized, a smooth and even running engine will .result and maximum power output from the en- 30 g'ine will be obtained. v It is accordingly an provide an improved piston (1) Shall eflect mixture of fuel and air in the object of my invention to which:-

combustion chamber with increased efficiency;

35. and

(2) Shall rate of burning of fuel and detonations within Additional objects 40 pointed out in the same taken in connection with the drawings wherein:

in an improved manner control the to prevent sudden impacts the cylinder.

of my invention will be following description of the accompanying Fig. 1 is a perspective view of my improved piston.

Fig. 2 is a section Fig. 3 is a section Fig. 4'is a plan viewof the crown of Figs. 5, 6 and '7 are bustion characteristics 0 my improved piston,

view in cross section of taken on line 2 of Fig. 3. taken on line 3-3 of Fig. 2. the piston. views illustrating the comresulting from the use of and includes in Fig. 5 a those parts which define the precombustion chamber and the main comjbu'stion chamber.

. The method of 55 provides for reliablefuel combustion disclosed herein and smooth operation of the f Serial No. 168,430.

Serial No. 168,430

Application Octoengine without detonation'or rough running, and permits the use of comparatively simple fuel injection nozzles operated by differential fuel pressure. During the many years in which compression ignition engines have been known, the combustion process in such engines has been considered as being dissimilar to, and presenting difierent problems than, the combustion process in spark ignition engines. In'this time, the only solution which has been offered to the problem of preventing. detonation and rough running in compression ignition engines has been the provision of complicated mechanical fuel injection apparatus requiring delicate adjustment for controlling the rate of fuel injection to control the combustion process;

In, my invention, fuel in the form-of a precombustion chamber which communicated with the main combustion chamber through restricted orifices. The injected fuel was to meet an incoming charge of air in the precombustion chamber, theoxygen therein being insufficient to support complete combustion, and the temperature being such as to cause ignition. Thus, the explosion in ,the precombustion chamber was to consume only part of the fuel, the remainder being shattered anddischarged in a gaseous state and at a high velocity into the main combustion chamber where the main supply of oxygen was to be available, 1 the charge being distributed throughout the main combustion chamber before the flame of the explosion was introduced. In the combustion chamber design, I intended to apply the method of preventing detonation and rough running which was known in spark ignition gasoline engines, but whose applicability in I employ the idea of injecting finely divided spray into a compression ignition engines had never, to my I constructed an engine designed to operate as D described. above and found that it operated successfully in accordance conceived; The design of the, precombustion with the method I had and main combustion chambers which afford this method of fuel combustion will now be described.

The precombustion chamber (Fig. 5) is formed within relatively thick'cylindrical wall IOI' of cylinder head 3 which has internal walls 80I, 802, and 803 01' decreasing diameters below nozzle 50I. Burner tube 804 is seated against shoulder 805 between walls 803, 802 and at the top engages wall 802 at 808. At its lower end, tube 804 has threaded engagement, with wall 803 at 801, and is provided adjacent its end with a plurality of orifices or outlets 808 providing for egress of fuel from the precombustion chamber to the combustion chamber. Slots 809 at the top of tube 804 provide means for threading the tube in wall IOI The inner walls of the burner tube converge conically from the top to a cylindrical portion closed at its lower end except for outlets 808.

It is to be noted from the above description that the precombustion chamber is formed of sections converging inwardly to provide for increased velocity of the fuel in passing threfrom to the combustion chamber. The relatively thick wall of the precombustion chamber aids in promoting proper thermal conditions therein. It is also to be noted that water in the cylinder head has free access to cylinder wall I0 I providing efllcient cooling of the precombustion chamber. The operation of the precombustion chamber during fuel combustion is described hereinafter.

My improved piston includes cylindrical wall portion 206 terminating in recessed head 201. The recessed head is especially formed in accordance with desired combustion chamber characteristics and is fully described in a later section;

Adjacent the upper portion of cylindrical portion 206 a plurality of peripheral recesses are provided in which rings 208 are seated. Rings 208 are of conventional construction. Adjacent the lower end of cylindrical portion 208 a single peripheral recess is provided, having oil ring 209 seated in the deeper portion thereof. The shallow portion of the recess is provided with a plurality of apertures 2II communicating with the interior of cylindrical portion 206 to provide oil outlets. Y

Substantially centrally of cylindrical portion 206, opposite apertured bosses 2I2 are'provided which are adapted to receive hollow wrist pin 2I3 which is held therein by plugs 2M. Pin 2I3 provides a journal for upper bearing 2I5 of connecting rod I29. Lubricant is transmitted to upper bearing 2I5 through conduit 2I6 mounted in connecting rod I29 and receiving lubricant from the lower connecting rod bearing not shown. Lubricant is transmitted through apertures 2I1 in bosses 2I2 from the shallow portion of the recess containing lower ring 208 to the bearing surfaces of wrist pin 2I3 in said bosses 2I2. From the foregoing description, it is seen that lubricant is brought by pressure through the connecting rod I29 to the upper connecting rod bearing 2I5, and from the bearing surfaces of the piston and the cylinder wall to wrist pin bearings 2I2 in the piston.

The combustion chamber is arranged to pro vide against detonation and rough running so that smooth operation of the. engine is possible without extremely accurate measuring of the fuel rate through the nozzle SM, and is formed between the cylinder head 9I and the crown 201 of the piston to provide a substantially central combustion chamber proper providing a concentrated volume of air into which fuel is injected from the precombustion chamber. Leading from the combustion chamber proper is a restricted space provided for a purpose described later in connection with the method of fuel combustion.

In the preferred form of the invention, the

crown of the piston'is machined to provide the combustion chamber. Piston crown 8I I is provided with a depression 8I2 slightly offset from the center thereof, and of a shape corresponding substantially to a segment of a sphere. This depression terminates in a peripheral wall, a. portion of which constitutes a relatively high peripheral ledge 8| 3 which extends around substantially one-half of the piston crown gradually widening as it approaches its extremities. The terminating walls 8 I 6 of the ledge 8I3 are vertical but arcuate in shape to accommodate intake and exhaust valves. The remaining portion 8I4 of the peripheral wall of crown 8| I is flat and of substantially uniform width until it approaches the vertical walls 8I6 where it broadens out gradually to a width equal to the length of the walls 8I6. The depression 8I2 is made to gradually merge into the flat portion 8I4 of the peripheral wall to provide for smooth flow of combustible mixture to the remote portions of the combustion chamber.

I The method of fuel combustion is designed to provide smooth operation and prevent detonation and rough running, the entire flow of fuel in both' liquid and gaseous states being controlled by utilizing the kinetic energy of the fuel under pressure. It is believed that the method can best be described by following the fuel from the time of its injection into the precombustion chamber through its burning in the combustion chamber. The upward movement of the piston compresses air in the main combustion chamber which has access to the precombustion chamber through holes or orifices 808. About 15 before top dead center of the compression stroke, fuel under pressure is introduced into the space defined by wall 80I of the precombustion chamber. The fuel is introduced in the form of a conical spray which strikes the walls of the burner tube 804, the temperature of which is controlled by the area of contact at 806 which transfers heat from the portion of the burner tube wall insulated from wall 802 by space 8I0. The interior of the conical spray is met by a stream of air forced up through orifices 808. At about 8 before top center, ignition takes place .in the precombustion chamber solely due to the vaporized condition of the fuel injected therein and the temperature existing therein. Inasmuch as the total volume of the precombustion chamber, i. e., within wall 80I and burner tube 804, is substantially 28 of the total combustion chamber space, only a limited amount of fuel can be consumed in the precombustion chamber space, such amount being substantially 20% of the fuel introduced for the full load charge.

The remaining fuel introduced is shattered by the explosion of the preliminary portion of introduced fuel, whereby the remaining fuel charge is gasified. The increased pressure existing in the precombustion chamber space, due to the explosion therein, causes a flow of gasifled fuel down through the channel defined by the burner tube 804 and out through openings 808 into the main combustion space. The fuel which emerges from openings 808 is of a gaseous nature, moving at a high velocity with controduced into a swirling current of air whereby thorough fuel distribution and high turbulence is obtained.

Heretofore, in compression ignition engines, it has been found necessary to provide extremely accurate measuring of the fuel rate through the injection nozzle to determine the correct rate of cumbustion in the main combustion chamber to prevent severe impacts on the wall of the cylinder by detonation waves, rough running of the engine. For convenience in describing the action of the fuel in response to the combustion chamber design disclosed herein, which obviates the necessity for extremely accurate measuring of the fuel rate, the space within the main combustion chamber is divided into seven zones. These zones are defined by spherical portions of increasing size having their center approximately at the discharge end of the burner tube and are numbered from I to VII in Figs. 5 and 6, being indicated in phantom lines.

The unburned gas as it enters zone I starts burning, and as further fuel is introduced, the flame spreads from zone I, to II, to [[1, etc. Due to the fact that ledge 8l3 (Fig. 5) is spaced closely to wall 9| of the cylinder head and extends around substantially half the circumference of the piston crown (as indicated in dotted lines in Fig. 6), a substantial portion of zone IV is occupied by said ledge BIS, only narrow space 826 (Fig. 5) remaining between ledge M3 and the cylinder head. This space represents substantially 17% of the total piston area and is cooled by virtue of its close contact with the cylinder head. Due to the close spacing and the cooling, no detonation wave can reach the wall of the cylinder adjacent ledge 8l3.

This condition, however, causes increased pressure within zone IV and if this pressure is not reduced, a detonation wave will strike the cylinder wall opposite to ledge M3. The restricted space between flat portion 8 of the piston crown and the cylinder head walls damps out the pressure wave, which is cooled due to the water space adjacent cylinder head wall 9 I. The construction of piston crown Bil adjacent wall 8 and cylinder liner 61 provides an increase in combustion chamber surface to volume ratio so that there is then the opportunity for cooling the gas so that the pressure wave does not strike the cylinder liner with a severe impact. ratio of combustion chamber surface to volume is illustrated in the graph comprising Fig. '1. In this graph the'zones are plotted as abscissas, while the ratios are plotted as ordinates. From an inspection of this graph it is seen that as initial combustion in the main combustion cham-v ber occurs, 1. e., in zones I and II, the ratio of surface to volume decreases and increases rapidly, being substantially the same at the beginning of zone III as at the end of zone I.

Thereafter the ratio increases rapidly through zones III and IV, increasing less rapidly through zones V and VI.

It is seen, therefore, that the method of fuel combustion disclosed herein eliminates detonation and rough running so that smooth operation'of the engine is posslble without extremely and to prevent The accurate measuring of the fuel rate through the injection nozzle 50!. arranging the combustion chamber to automatically provide the desired combustion rate'and at the same time damping and cooling the flame front .as it advances toward the cylinder wall.

I, therefore, claim as my invention:

1. A piston having a crown including a ledge extending around a substantial portion of the circumference thereof and terminating in end walls, the remaining portion of the circumference of said crown being fiat and lower than said ledge, said circumferential portions encompassing a depression having the contour of a portion of a sphere.

2. A piston having a crown formed with a depression offset with respect to the center of said piston, said depression having the contour of a portion of a sphere, a portion of the peripheral wall surrounding said depression rising to, a different elevation than another portion of said peripheral wall.

3. A piston having a crown formed with a depression having substantially the contour of a portion of a sphere, said depression being offset with respect to the center of said piston, a portion of the peripheral wall surrounding said depression rising to a different elevation than another portion of said peripheral wall, said depression gradually merging with the wall of lower elevation.

4. A piston having a crown formed with a depression offset with respect to the center of said piston, said depression having the contour of a portion of a sphere, a peripheral wall surrounding said depression, a portion of said peripheral wall being higher than another portion and having its end boundaries shaped to provide clearance for inlet and exhaust valves.

5. A piston having a crown formed with a depression ofiset with respect to the center of said piston, said depression having the contour of a portion of a sphere, a portion of the peripheral wall surrounding said depression rising to a different elevation than another portion of said peripheral wall, said crown in combination with a cylinder head and cylinder wall providing a combustion chamber in an engine wherein the wave front of an exploding mixture will cool sufllciently before reaching the cylinder wall to preclude detonation.

6. A piston having a crown formed with a depression offset with respect to the center of.

said piston, said depression having the contour of a portion of a sphere, a peripheral wall surrounding said depression, a portion of which wall rises to a higher elevation than the remaining portion and terminates in vertical end walls which are arcuate in shape to accommodate inlet CARL G. A. ROSEN.

This is accomplished by i 

